• inflammation
• cardiovascular diseases
• systemic vasculitis

In the first months of COVID-19 pandemic, paediatricians were not much involved in the management of the illness. Reports from China had shown that relatively few children and adolescents were affected, and that most of those who were infected had experienced milder disease compared with adults.1 2 The same trend was initially seen after the spread of COVID-19 to Western countries.3 4

However, between April and May 2020, a rise in the number of children and adolescents with an acute multisystem hyperinflammatory state fulfilling full or partial criteria for Kawasaki disease (KD),5 although frequently accompanied by unusual or less common symptoms, such as abdominal pain, diarrhoea and myocardial failure, was noticed in European and North American countries or regions mostly hit by the COVID-19 pandemic.6–9 A number of these children needed urgent intensive care treatment due to the development of toxic shock syndrome, leading to multiorgan failure and circulatory shock, usually of myocardial origin, and some of them had signs of macrophage activation syndrome (MAS). Markers of inflammation were elevated, with neutrophilia, prominently increased C-reactive protein, interleukin (IL)-6, D-dimer and ferritin levels, and hypoalbuminaemia. Lymphopenia and relative thrombocytopenia were often present. Management was based on the administration of anti-inflammatory treatment, which included intravenous immunoglobulin (IVIG) and glucocorticoids. In some instances, IL-1, IL-6 or tumour necrosis factor inhibitors were given. Some, but not all, of these patients tested positive on swabs or serology for SARS-CoV-2 or were exposed to potential contact with a household member affected with COVID-19.

Alerts have been issued by national health authorities and paediatric scientific societies to raise awareness of this emerging syndrome in the medical community.10–14 This condition, which has been named ‘Paediatric inflammatory multisystem syndrome temporarily associated to SARS-CoV-2 infection’ (PIMS-TS) in the UK, ‘Multisystem inflammatory syndrome in children’ in …